Attached are two styles of the midrange's crossovers. As can be seen, they are both capable of producing nearly identical responses. However, I still wonder what the pros and cons are between the two. Could any experts please explain them?
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I see you've made the small adjustments necessary to show that they are capable of the same transfer function. Linear analysis suggests the primary difference is the impedance. If that doesn't create a significant/noticeable difference with your equipment, as it shouldn't necessarily do, then these should behave similarly.
And the crossover B should be preferable because of its higher impedance, am I correct?
I looked at the plots and then at the schematics, and this is what it looked like to me. I have a feeling we talked about this process in the past 😉
Anyway, since I didn't include the phase responses in the first post, are phase plots required when the frequency responses are the same?
You don't need phase if both responses are minimum phase, it will be the same.. However note that if the response changes out of band it can bring phase variations in the passband, so it's recommended to check anyway especially if you can't see the response on a wide plot.
Phase angle of the impedance may be different as well. It's also not on your plot. This shows how capacitive/inductive the load is.
If the response is the same outside the passband, so you have to look at higher and lower frequencies and levels.
A good teaching example is where you try to match the response of a higher order rolloff using a single resonant circuit. Response will be correct where it’s important but phase won’t keep up. (If that doesn’t make sense I can show an example at a later time)
A good teaching example is where you try to match the response of a higher order rolloff using a single resonant circuit. Response will be correct where it’s important but phase won’t keep up. (If that doesn’t make sense I can show an example at a later time)
This is within my interesting. I’ve been researching about it at present. It began by the curiosity of a commercial speaker whose midrange is crossed over at quite low frequency.
The midrange is 6 Ohms nominal and its high-pass filter is second-order formed by a series 33uF capacitor and a shunt 2.6mH inductor. The manufacturer used this filter in various models whose midrange drivers resemble. By calculation, the filter resulted in about 550Hz corner frequency which is considered to be so low for the 2” midrange dome drivers.
And I’m suspecting the designer may have done a trick on that design. He probably made a steeper acoustical slope—24dB per octave—by using an electrical slope—12dB per octave—combined with a natural roll-off of the driver whose enclosure is already sealed type—also 12dB per octave.
Accordingly, please provide your example.
D
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Out of interest, can you include the phase response plots? It would be interesting to see where the two circuits might start to vary from each other. That probably occurs above 10kHz or so, as that's where the slopes begin to diverge. I'd guess that below 10kHz there will be no significant difference, give or take a few degrees.
For a minimum-phase system, I don't see how out-of-band responses can bring significant phase variations in the passband. Can you provide an example?
Below is an example of adding a −10dB dip at 6kHz to a 2nd-order bandpass filter with cutoff frequencies of 300Hz and 3000Hz. Here the passband is a decade wide. In this example, there is clearly a significant effect of the 6kHz dip imprinted on the phase response. However, a 10dB dip is very extreme.
If we introduce a much smaller dip, this time −2dB, we get much less of an effect, bordering on the insignificant in the passband.
If we introduce a much smaller dip, this time −2dB, we get much less of an effect, bordering on the insignificant in the passband.
Is that because the effect of the resonant circuit is local in nature?
The second-order filter does provide a reasonable amount of attenuation to a driver whose resonance frequency might be around 400Hz or so. Whether this is usable in a design in a reliable manner depends a bit on the sensitivity of the driver and the power handling that's required.
Is that really a trick? It's a reasonable approach to use in order to help minimize the width of the crossover transition zone in the design.